New Tool to Predict Delayed Allergic Reactions in Children

Posted on Monday, June 22, 2015

Depending on the severity of their initial allergic reaction, children are more likely to have a repeat, delayed anaphylactic reaction from the same allergic cause. These were the findings of the first pediatric study to look at predictors for this phenomenon, which was published today in Annals of Allergy, Asthma & Immunology.

Anaphylaxis is a severe allergic reaction that occurs quickly and can be deadly, and some children are at risk of delayed (“biphasic”) anaphylactic reactions.  Delayed reactions occur when the initial symptoms of the allergic reaction go away, but then return hours or days later without re-exposure to the initial substance that caused the reaction.

A study conducted by the Children's Hospital of Eastern Ontario (CHEO) Research Institute looked at the frequency and severity of biphasic allergic reactions.  The researchers reviewed  484 patient records and found that the incidence of biphasic reaction occurred in 15% of the study population, and that two-thirds of these biphasic reactions occurred within six hours of the onset of the initial reaction. At least half of the biphasic reactions were serious in nature and required treatment with epinephrine.

The study revealed that biphasic reactions were more likely to occur if the initial allergic reaction was severe or had not been treated with epinephrine. Moreover, the anaphylaxis tended to be more severe when the administration of epinephrine was delayed.

“The key message here for patients, parents, caregivers, teachers, and first-responder health professionals is: to prevent an anaphylactic reaction from worsening, administer epinephrine immediately after the onset of the early symptoms of an allergic reaction,” said Dr. Waleed Alqurashi, who is an emergency medicine physician at CHEO, and assistant professor at the University of Ottawa. “Our team has created an evidence-based prognostic tool so that physicians can monitor the more serious cases appropriately."

The team identified five independent, evidence-based predictors of biphasic reactions in children, including:

  1. Delay in presentation to an emergency department (or delay in administering epinephrine) of more than 90 minutes from the onset of the initial allergic reaction
  2. Wide pulse pressure at triage
  3. Treatment of the initial allergic reaction with more than one dose of epinephrine
  4. Respiratory distress that requires administration of inhaled salbutamol in the emergency department
  5. Children between the ages of 6 and 9

“It's clear that children with severe initial reactions would benefit from a prolonged period of observation in the emergency department,” continued Alqurashi. “On the flip side, knowing what to look for helps to better utilize resources so that children with mild allergic reactions, who do not match any of the identified predictors, can go home sooner.”

The study, entitled Epidemiology and clinical predictors of biphasic reactions in children with anaphylaxis, was conducted by clinical investigators and epidemiologists from the CHEO Research Institute, the Ottawa Hospital Research Institute, University of Ottawa, and Memorial University.

Researchers reviewed the health records of patients who presented with anaphylaxis at the emergency departments of CHEO and the Hospital for Sick Children (SickKids). The diagnosis was based on the established diagnostic criteria of the National Institute of Allergy and Infectious Diseases and the Food Allergy and Anaphylaxis Network.

About the CHEO Research Institute

The CHEO Research Institute coordinates the research activities of the Children's Hospital of Eastern Ontario (CHEO) and is affiliated with the University of Ottawa. Its three programs of research include molecular biomedicine, health information technology, and evidence-to-practice research. Key themes include cancer, diabetes, obesity, mental health, emergency medicine, musculoskeletal health, electronic health information and privacy, and the genetics of rare disease. The CHEO Research Institute makes discoveries today for healthier kids tomorrow. For more information, visit

About the University of Ottawa—A crossroads of cultures and ideas

The University of Ottawa is home to over 50,000 students, faculty and staff, who live, work and study in both French and English. Our campus is a crossroads of cultures and ideas, where bold minds come together to inspire game-changing ideas. We are one of Canada's top 10 research universities—our professors and researchers explore new approaches to today's challenges. One of a handful of Canadian universities ranked among the top 200 in the world, we attract exceptional thinkers and welcome diverse perspectives from across the globe. For more information, visit

Media inquiries

Kina Leclair
University of Ottawa
Office: 613-562-5800 (2529)
Cell: 613-762-2908

Adrienne Vienneau
CHEO Research Institute
Office: 613-737-7600 (4144)
Cell: 613-513-8437

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